After 85 years, Marie Runyon is still all about sticking it to the FBI, pompous politicians and anyone else who ticks off the longtime New York radical.

So, the white-haired Southern lady threw a bash in her Morningside Drive apartment the other day – in front of communists, socialists, leftists and even a few journalists – to celebrate the opening of a package the size of the Manhattan phone book.

Inside was the voluminous file the FBI had maintained on Runyon for years.

“I have a lot of friends who are concerned about what the FBI does, and would like to be in on the opening of this great big, fat thing,” said Runyon, who also had the moment captured by the documentary-film crew that has followed her for the past year.

“I said to her, ‘Marie, you spent a year and a half getting this [released], and now you’re having a party. You’re not taking this serious?’ ” said Runyon’s friend Madeline Amgott.

“Well, I’m odd,” said Runyon, whose last Christmas letter to friends noted that she was arrested “only once” in 2000. “Very odd.”

Runyon, a former one-term state assemblywoman, apparently drew the FBI’s attention because of her involvement in Vietnam War protests, Black Panther fund-raising, anti-nuclear activism, housing rights, and many, many other movements over six decades.

Her friends gasped when she opened the box, said “This is it, y’all!” and hoisted the 423 pages the FBI sent her.

The agency won’t release the other 248 pages it has on Runyon, who in dress, decorum and drawl seems more the afternoon-tea hostess than firebrand radical.

“Oh, I’m thrilled. I can’t wait to read all of this,” Runyon told them. “Can you believe that you guys paid for all this?”

What taxpayers paid for – or at least what hasn’t been blackened out by censors – is mostly a collection of the minutes of community group meetings discussing various fund-raisers, protests and hootenannies.

But there is the occasional cloak-and-dagger reference to “sources” and “special agents.” The documents reveal that her building’s superintendent once searched her trash at the FBI’s behest, and that agents visited her undercover on the pretext of joining one of her causes.

“Marie Runyon turned out to be a middle-aged white woman whose apartment was decorated with pictures of Eldridge Cleaver, Mao Tse Tung, and other dissident notables whose faces he [an informant] recognized but whose names he did not know,” reads an FBI report of June 23, 1969.

Norman Siegel, who is on leave as executive director of the New York Civil Liberties Union, said the party was bittersweet justice for a woman he called “a character, at a time when we don’t have many characters . . .

“Why the heck were they spying on her? Marie’s not a threat to anybody except to people who are violating people’s rights.”